Python Challenge

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Python is a general-purpose programming language. This means that you can create various types of software in it: write web applications, scripts to improve the operation of the system, analyze large data sets, create artificial intelligence. There are really many applications for Python.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If you do not have any programming experience, Python is a good choice for a start: it's an easy language for beginners, but at the same time, it offers great possibilities. It is designed so that the programmer does not have to "fight the syntax", he only solves problems. Python is used by small, medium and large companies: Google uses this language extensively in its search engine and on YouTube. Instagram and Pinterest are written entirely in Python!
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Python's history speaks best for its potential and flexibility. When it was created in 1991, many branches of computer science, in which it is most extensively used today, were only starting to develop. Apart from a handful of enthusiasts, nobody seriously thought about them!

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Each program - regardless of the language used - must store the data it will use. This may be, for example, the user's name or the price of the purchased movie DVD. We store data in special constructions which we call variables.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In Python, variables are defined as follows:

# variable declaration
user = "Anakin Skywalker"
price = 30
price_with_vat = price * 1.23

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See an example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT1sample0EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Example of variables</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Let's start with the explanation from the # sign: it indicates a comment and it's for describing the code. Everything you see in the line of code after this sign will not be executed by the computer.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Please note the following:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">each variable has its own name (<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">user, price, title<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">),
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">there is an<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> equality sign<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> after the name (this is the assignment operator)
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">after the equality sign, the<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> variable value<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> follows.
</li>
</ul>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the above example, we have defined the following three variables:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">variable named <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">user<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">, in which the "Anakin Skywalker" (Star Wars FTW!) string is stored,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">a variable named <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">price<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">, in which the number 30 is stored,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">at the end we have the variable <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">price_with_vat<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">, which stores the value <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">36.9<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> (note that we use the American notation, where the integer part is separated by a period, not a comma!). This value was created by multiplying the value stored in the variable <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">price <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">by 1.23.
</li>
</ul>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The simplest way to imagine a variable is a box with a label. We can store different items in the box - in our case, various information. In Python, first we write the name of the "label", and after the equality sign - the contents of the "box". We can replace the contents in the box, e.g.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">From now on, the variable <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">user<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> stores the value "Darth Vader".

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Important note:<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> if you do not declare a variable - you can not use it! When trying to use a variable that is not defined, you will get an error!

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Call it as you want. :) Although, as everywhere, Python programmers have certain rules:

<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">use letters (remember that Python distinguishes between uppercase and lowercase letters : <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">A<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> is something completely different than <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">a<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">!)
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">you can use digits (but the variable name can not start with a digit),
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">the only character that is not a letter or digit, and at the same time is allowed in the variable name, is the <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">underscore sign.<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">&nbsp;
</li>
</ul>
&nbsp;

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Variables can store different data. The most popular are:

# variable name stores a string with the name, e.g.
name = “Anakin”

Note that the string is stored in quotes.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">A number can be an integer (abbreviated as int) or a floating point number (float)

# int type variable named age stores the user’s age
      age = 45
 
# float type variable stores the user’s height 
      height = 1.88

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">It can take two values:

<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre;" aria-level="1">True</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre;" aria-level="1">False</li>
</ul>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">(both values must necessarily be capitalized).

# logged_in logical variable stores the information
# whether the user is logged in or not:
# (True - yes, False - no)
logged_in = True

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Sometimes we want the variable value to be empty, just like a box can be empty. Zero is not a solution here, because zero is an int value. This value is None (also capitalized).

# variable with an undefined value
# stores the knowledge of Jon Snow
jon_snow_knows = None

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The data exists to inform the user. We can therefore display them on the screen with the print() statement.

# An example so popular that everyone knows it and does not need to be explained.
# Just pay attention to the brackets: they are obligatory!
print("Hello World!")
 
# and here we display the age of Darth Vader
# defined in the examples at the beginning of the lesson
print(age)
 
# and now something more difficult - a combined message:
# we display many variables and even strings that are not
# placed in any variable. Pay attention to commas
# separating successive values.
print(name, "is", age, "years old.")

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See an example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT1sample1EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Example of communication with a user</a>

Define a <span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #000000; font-weight: bold; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: baseline; white-space: pre-wrap;">product variable, assign the value <span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #000000; font-weight: bold; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: baseline; white-space: pre-wrap;">"Computer" to it<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #000000; font-weight: bold; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: baseline; white-space: pre-wrap;">. Then define a <span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #000000; font-weight: bold; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: baseline; white-space: pre-wrap;">net_price variable - assign the value of <span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #000000; font-weight: bold; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: baseline; white-space: pre-wrap;">1500 to it<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #000000; font-weight: bold; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: baseline; white-space: pre-wrap;">. Display a message on the screen with the name and the net price of the product.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Solve the task here: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT1exercise1EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 1</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT1exercise1solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 1</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Look at the code written in <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT1exercise2EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">task 2.</a><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> Why doesn't it work? Correct it and run it. Read the error message that will be displayed carefully, you will find instructions there.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If you are still having problems, see task 1.
Need a hint?
See solution:<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT1exercise2solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">solution to problem 2</a>

Look at the task code of <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT1exercise3EN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #0563c1; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">the third task.</a> There are four variables of the logical type and one numeric variable. Each of them corresponds to a particular kind of weather. Look out the window, check the weather and set the variables accordingly. Run the program.

Variables

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Every programming language allows you to do arithmetic operations, and Python is no exception. Every basic calculation is written intuitively:

<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">the + sign denotes addition,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">the - sign denotes subtraction,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">the * sign denotes multiplication,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">the / sign denotes division.
</li>
</ul>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The above signs are called operators. Their use is very intuitive:

# We define a variable in which we store the current year
actual_year = 2018  

# We define a variable in which we store the year of release
# of the first version of Python
python_year_of_birth = 1991

# And here we calculate how old Python already is
# To do that, we'll use the operator - (minus)
python_age = actual_year - python_year_of_birth

# What's the use of data if we can't read them?
print("Python is", "python_age", "years old.")

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2sample1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">arithmetic operators</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Logical, isn't it?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Let's look at one more example then:

# What will happen?
my_variable = 100 / "dear!"

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">After running the program we will get the following error:

Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for /: 'int' and 'str

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">What happened here?
Python tried to divide the number 100 by the string "dear!". Is it possible to calculate it? Of course not! So an error was reported. Read the error message carefully, namely its last line. It means that Python cannot use the division operator for int and str data.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">A very interesting operator, available to the programmer is the operator %, or modulo. This is the remainder of a division. So if we divide 16 by 5, according to the rules of arithmetic, we get the result of 4 and remainder 1. In Python we can write this operation as follows:

# Calculating the modulo, which means dividing with remainder
my_val = 16 % 5
print(my_val)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The program will display the number 1 on the screen.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Imagine you're writing a computer game. When you shoot down an enemy ship in it, you get 100 points. This means that the number 100 should be added to your current score. How do I do this? It's very simple:

# Define a score
score = 0
 
# Add 100 points to your current score.
score = score + 100 # score is the name of the variable, 
                    # In which we store the score of the game
 
print(score)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2sample2EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">increasing the value of a variable</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Such notation means that the score variable is based on the current value of the score variable and 100 is added to it.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The same result can be achieved by using a shortened notation:
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">score += 100

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">It works the same way as the previous example. The += operator is the so-called increment operator. In addition to the increment operator, there is also the decrement operator -=, which subtracts a value from the current value of the variable.

What does your intuition tell you? Is it possible to add strings to one another? What happens when you add "Wars" to "Star"?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example<a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2sample3EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">: text operators example</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The result will be "StarWars". So you can!
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> And can you multiply a string by a number?&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If you have the courage, try to execute the following code and see what happens:
See example: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT2sample4EN#main.py"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">multiplying string by number</a>

# at your own risk! ;-)
spell = "Bloody Mary " * 3
print(spell)

Look at the previous chapter: we defined the product and its net price, saving them in the variables&nbsp; product and net_price respectively. Now calculate the gross price of the product at a VAT rate of 23% (or 0.23). Save the result in the gross_price variable. Then, using the print instruction, display the full product information: name, net and gross price.
 <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task one: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2exercise1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">task 1</a> <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2exercise1solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">solution to Task 1</a>
&nbsp;

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Look at the code. You will find the following variables there:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
in_left_hand_i_have_a_pen = False
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
in_left_hand_i_have_a_phone = True
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
in_right_hand_i_have_a_mug = True
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
in_right_hand_i_have_a_spoon = False
</li>
</ul>
&nbsp;

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Then make appropriate logical operations and save their results to variables, then display the results on the screen:
<ol style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: decimal; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">I have a pen in my left hand and a cup in my right hand.
</li>
<li dir="ltr" style="list-style-type: decimal; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
I have a cup in my right hand or a spoon in my right hand.
</li>
<li dir="ltr" style="list-style-type: decimal; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">I don't have a phone in my left hand.
</li>
</ol>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;">Go to task 2: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2exercise2EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 2</a>
 See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT2exercise2solutionEN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">solution to task 2</a>
&nbsp;

Declare a numeric variable, give it any value that is a natural number. Then check if the number is even: if the result of dividing it modulo 2 is 0 - it is even, if 1 - it is not. Display a message that will contain a description of the operation: "&lt;number&gt; % 2 = &lt;result&gt;" <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task three: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2exercise3EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 3</a> <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2exercise3solutionEN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 3</a>
&nbsp;

Declare a variable named number, give it any numeric value. Try dividing the variable by zero. Read the error message. <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task four: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2exercise4EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 4</a> <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT2exercise4solutionEN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 4</a>

Arithmetic operators

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Is it possible to assign multiple values to a variable?
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Imagine that you are writing software for your online store and reaching the point where you need to program your shopping cart. With your current Python knowledge, are you able to create a variable&nbsp; which will enable you to store multiple products?
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">No, because the variable types you know only allow you to put a single object "in a box". Programming languages, such as Python, deal with this problem by providing programmers with so-called lists.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">A list is a special type of variable that allows you to "throw more than one thing into the box".

# The current content of my pocket (numbers are coins)
my_pocket = ["phone", 0.05, 0.05, 0.02, "old receipt"]
print(my_pocket)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The variable my_pocket contains a collection of different elements. The data type of this variable is a list. Note the square brackets: it opens and closes the list. Inside the brackets there are subsequent elements of the list, separated by commas. Note that these elements are not of the same type - in our example, they are strings and numbers, but in fact, each element in the list can be of any type: number, string, logical value (True/False), None, and even another list!
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The list is organized. This means that on the first place of our sample list there is the word "phone", on the last place there is the word "old receipt". Each element has its own position in the list, which programmers call an index.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Now focus, because there is an important thing to remember: we number the list starting from zero, instead of one! This means that the index of the "phone" element is 0, the number 0.05 - 1 and so on until the "old receipt", which has the index 4!

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The easiest way to remember this is to compare the list to a tenement house, as in the example below:

#221b Baker Street!
baker_street_221b = ["Mrs Hudson", "Holmes", "Watson"]
print(baker_street_221b)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See the example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3sample2EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Example of a list</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Mrs Hudson lives on the ground floor (i.e. the floor with number 0), Sherlock Holmes on the first floor, and Dr. Watson on the second floor.

Absolutely! You just need to know the number of the element in the list. If in the example with Sherlock we want to download Dr. Watson's data, we need to know the number of the floor on which he lives. Doctor lives on the 2nd floor, his index on the list is therefore 2.

# display Dr. Watson's data
print(baker_street_221b[2])

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See the example: <a href="https://replit.com/@CodersLab/PYT3sample3EN">Example of retrieving an element</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Note that we displayed the doctor's data by entering the name of the variable from the list, and then immediately, in square brackets, we followed it with the index of the element we wanted to retrieve. Similarly, we will display the data of Mrs. Hudson from the ground floor like this:

# Mrs Hudson
mrs_hudson = baker_street_221b[0]
print(mrs_hudson)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See the example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3sample4EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Example of accessing an element</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Isn't it simple?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Yes, just use the append() method.

baker_street_221b.append(“Lestrade”)
print(baker_street_221b)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See the example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3sample8EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Example of adding a new element</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Inspector Lestrade moved into Mrs. Hudson's house. He took up another floor and... our analogy is falling apart here, because in Python it looks like every new element lengthens the list. So it's as if every tenant moving out demolished their floor and every new one added another one. ;)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">To check it, just use the len() function, where the name of the list is given as a parameter: 
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3sample9EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">checking the number of list elements</a>

Of course not! If we ask Python about the inhabitant of the tenth floor:

# 10 floor!
print(baker_street_221b[10])
 
We get:
 
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
IndexError: list index out of range

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Declare a list named the_beatles. Include the following members in the list: "John Lennon', 'Paul McCartney', 'George Harrison', 'Stuart Sutcliffe'. Display the content of the list on the screen. Then add a new band member, whose name is Pete Best. Display the content of the list on the screen again.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task one: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3exercise1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 1</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT3exercise1solutionEN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">solution to Task 1</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Stuart Sutcliffe left the band before the first album was released (he died shortly afterward). Remove the appropriate element from the the_beatles list. Display the new band's line-up on the screen.
&nbsp;
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task two: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3exercise2EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 2</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT3exercise2solutionEN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 2</a>

Soon afterward, three musicians, persuaded by the manager, decided to fire the drummer Pete Best and hire Ringo Starr to replace him. Replace the appropriate element on the the_beatles list. Display the new band's line-up on the screen.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task three: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3exercise3EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 3</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT3exercise3solutionEN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 3</a>
&nbsp;

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">FInally, display the band's line-up on the screen, but do not display the entire list. Instead, display all the members individually, each in a new line.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task four: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3exercise4EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 4</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT3exercise4solutionEN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 4</a>
&nbsp;

Lists

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Imagine that we have a variable with a list of Star Wars characters:

# Star Wars!
star_wars = ["Luke", "Leia", "Han", "Vader", "Obi-Wan", 
  "Chewie", "R2D2", "C3PO", "Emperor", "Jabba",
  "Lando"]

The star_wars variable stores a list of elements that are strings. In this lesson we will learn how to operate on lists in Python.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">What happens if we give a negative index?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4sample1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">negative index</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The program will display "Lando".

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Index -1 simply means "take the first element from the end". Similarly, index -2 will return Jabba, -3 - Emperor, -4 - C3PO, and so on. Index -100 will throw an error, because the list doesn't have so many elements.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">We can download a fragment of a list by entering two indices indicating the start and end of the desired fragment. Separate them by a colon, just like you see below:

# extract from the list
extract = star_wars[2:5]
print(extract)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4sample2EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">a fragment of the list</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The result will be:

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Something's wrong here, isn't it? Since the initial and final indexes are given in brackets, it should display characters from Han to Chewie, inclusive!

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Well, no. In Python the final index is the one that is no longer in the range. Simply put, add 1 to the index of the last element you want to extract. So star_wars[2:5] will extract&nbsp; the elements of the star_wars list with indexes 2, 3, 4, but not the one with index 5!

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If you omit the list index (<a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4sample3EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">see example</a><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">):

ch1 = star_wars[4:]
ch2 = star_wars[:6]
print(ch1)
print(ch2)

the following will happen:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre;" aria-level="1">in the ch1 variable, there will be star_wars list elements displayed starting from the element with index 4 to the last element,</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre;" aria-level="1">the ch2 variable will contain star_wars list elements starting from the element with index 0 to the element with index 5 (remember that the end index does not fall into the range)</li>
</ul>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">You can also use negative indexes in the ranges (<a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4sample4EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">see example</a><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">):

ch3 = star_wars[-4:]
print(ch3)
 
Result:
 
['C3PO', 'Emperor', 'Jabba', 'Lando']
 
That is, from the fourth element from the end to the last element.
 
ch4 = star_wars[1:-5]
print(ch4)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4sample5EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">negative indexes</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Result:

['Leia', 'Han', 'Vader', 'Obi-Wan', 'Chewie']

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Note that the fifth element from the end is R2D2, but this element is out of range.

Python is designed so nicely that it even allows you to extract from the list not only a few , but for example every second, every third element - even counting from the end! You only need to add another parameter in square brackets (step), also separated with a colon.

# We take every second element, starting with the first,
# Up to and including the sixth.
ch5 = star_wars[1:7:2]
print(ch5)
 
# ...and here we take every third one from start to end:
ch6 = star_wars[::3]
print(ch6)
 
# Now we take every other element starting from the second from the end 
#  up to the second from the beginning:
ch7 = star_wars[-2:2:2]
print(ch7)
 
# ...and now the best: we reverse the order of the list:
ch8 = star_wars[::-1]
print(ch8)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4sample6EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Extracting elements</a>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Brilliant, isn't it?
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">But that's not all!
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Let's go back to the beginning of the previous lesson, where we called the list a collection. A collection in computer science is an object that can store any number of other objects. So, in Python, a list is a collection. What else is a collection?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The strings?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Yes! In Python a string is also a collection of single characters! And just as we can navigate a list, extract small fragments from it, reverse it - the same can be done with strings.

# Let's take the first character from the string
txt = “A long time ago in a galaxy far, far away…”
print(txt[0])
 
 
Result:
A
 
...and now we will extract the second word:
 
word = txt[2:6]
print(word)
 
Result:
long
 
And now let's reverse the string:
print(txt[::-1])
 
Result:
...yawa raf ,raf yxalag a ni oga emit gnol A

See example: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT4sample7EN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">text operations</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Analyze the code. Here you will find a list of all The Beatles' albums, sorted from the oldest (index 0) to the newest. Display the band's first and last album.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task one: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 1</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise1solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 1</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Display the first five albums of the band on the screen.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task two: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise2EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 2</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise2solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 2</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Display on the screen all albums from third to seventh inclusive.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task three: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise3EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 3</a>
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT4exercise3solutionEN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 3</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Now, display every second album, from the first to the last.<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">&nbsp;
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task four: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise4EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 4</a>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise4solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 4</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Finally, display all the albums from the oldest to the latest (use reversing of the array).
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task five: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT4exercise5EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 5</a>
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT4exercise5solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 5</a>

List operations

<span style="font-size: 16pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Loops
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Imagine you peel potatoes. You take the first potato from the bag, peel it, put it in the pot. Then take another potato, peel it, put it away - until all the potatoes are peeled. Now, imagine that you have to program the robot that does this. How do you get down to it?
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The simplest yet least effective idea is to write as many operations of this sort: take the potato - peel - put in a pot, as there are potatoes in the bag. It's a bad idea, because:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">first of all, it is a one-time action (because next time we will have a different number of potatoes and we will have to modify the program),
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Secondly, this is not efficient because if you peel potatoes for an army regiment, you have to write several hundred such repetitions* manually. 
</li>
</ul>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The easiest and most effective way is to write the program the following way:
<ol>
<li dir="ltr" style="line-height: 1.295;" role="presentation"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">if there are still potatoes in the bag:
<ol>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Take a potato,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">peel it,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">put it in the pot,
</li>
</ol>
</li>
<li><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">go back to point one.</li>
</ol>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">&nbsp;<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;"> 
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">This way will always work, no matter if we have three potatoes to peel, ten or one hundred and fifty.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">* Cyclic repetition of a set of actions, e.g. take a potato - peel it - put it in the pot, is called an iteration.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the Python language (and in all others too) there are special structures called loops. Loops are the repetitions of a set of actions. There are many ways to write loops, but we Python coders, most often use for-in constructions.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">To explain how such a loop works, let's consider an example:

# a bag of potatoes
bag = [“potato 1”, “potato 2”, “potato 3”, “potato 4”, 
       “potato 5”]
 
# we make a loop
for potato in bag:
    print(potato, “peeled!”)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The for - in loop is created as follows:

<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">First, we have the keyword for,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">then we declare the variable in which successive elements from the collection will be placed; in our case it is the potato variable, in which successive values from the bag list will be placed,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">then we write the keyword in,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">At the end we state the collection, which we iterate through.
</li>
</ul>

# For each potato in the bag, do the following
for potato in bag:

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Pay attention to the colon at the end of the code line. It is mandatory!
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Print instruction
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">What is to happen as the next step in the loop (peel the potato) is written in the code block (where there is the print instruction). This block of code is the so-called loop body, all the instructions are to be repeated as long as the potatoes are in the bag. Note that the print line is indented in relation to the for instructions. This indentation is mandatory. It can be 1 tab (it will work, but is reluctantly accepted by programmers), or several spaces (good&nbsp; solution - preferably 4 spaces). All the instructions inside the loop should be indented!

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The loop will take another element from the list and this element will be assigned to the potato variable. Then the body of the loop (i.e. the code in the indentation) will be executed. After the indented code is finished, another list element will be taken and assigned to the potato variable. This will be done as long as there are some other elements in the bag list.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">This solution is universal! If the bag list contains 100 potatoes, it will be done 100 times. If only one, it will be done only once. If the list is empty - it won't be done even once, because there won't be any potatoes in the bag! :)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">We are not going to peel potatoes in the tasks. We will work with cooler things, namely The Beatles band. Take a look at the code. You will find there a list of songs from the album "Please Please Me". In a for - in loop, iterate through the song list and display each song separately.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task one: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT5exercise1EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 1</a>
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT5exercise1solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 1</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Look at the code. You will find there a list named please_please_me_time, which contains the duration of each song from the album "Please Please Me" in seconds. In a&nbsp; for - in loop, iterate through this list and sum up all the times. Display the result on the screen.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">How to do this?
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">First declare a variable, name it somehow, e.g. result, and assign the initial value of 0 to it. Then, in the body of the loop, add the value of the next loop element to the variable result.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to the second task: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT5exercise2EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 2</a>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT5exercise2solutionEN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 2</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">It's time for something more difficult: repeat the code from the first task, but instead of displaying subsequent strings from the please_please_me list, do the following:
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Display the title of the song, the text "\t" (the character \t means tab) and the duration of the song on a single line.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task three: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT5exercise3EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 3</a>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT5exercise3solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 3</a>

Loops

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the lesson about operators we got to know logical operators. You can ask the computer for any value and it will tell you if our value is true or false.
 See example: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT6sample1EN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">conditions</a>

age = 44
print(age >= 18)  # only for adults!
 
 
The result will be:
True

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The forty-four-year-old is definitely older than an eighteen-year-old, so the result is the logical value "true".

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Thanks to logical operations we can introduce conditions into our program. If the user's age is less than 18, tell him to come with parents.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In Python we execute it with the if statement. After the if keyword, the condition follows.

age = 15
 
if age < 18:
 print(“Come with your parents!”)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a href="https://replit.com/@CodersLab/PYT6sample2EN">if statement</a>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Pay attention to the colon and code block indentation which we know from the previous lesson! The rules are the same as for a loop.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">This piece of code should be read as follows:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If age &lt; 18:
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">write "Come with your parents!".
</li>
</ul>
&nbsp;
We already know how to turn out a teenager - now we should welcome an adult. We use the else clause for this.

age = 26
 
if age < 18:
 print(“Come with your parents!”)
else:
 print(“Welcome, have a good morning.”)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT6sample3EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">using else</a>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Else means "otherwise". The whole statement should be read as follows:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If age &lt; 18:
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">write "Come with your parents!"
</li>
</ul>
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Otherwise:
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Write "<span style="font-size: 11pt; font-family: Consolas,sans-serif; color: #393a34; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Welcome, have a <span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">good morning."
</li>
</ul>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Pay attention to the colon and the indentation after else.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The last example will be a situation in which we want to treat a person younger than 18 years of age differently from an eighteen-year-old and an older person:

age = 18
 
if age < 18:
 print(“Come with your parents!”)
else if age == 18:
 print(“You’ve finally grown enough for our application.”)
else:
 print(“Welcome, have a good morning.”)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT6sample4EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">the use of else if</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Take a look at the else if instruction. This is an instruction you should read: "If the previous condition is not met, check this one. This means that the whole thing should be read as follows:

<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; margin-left: 52.8pt;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If age &lt; 18:
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; ; margin-left: 52.8pt;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">write "Come with your parents!".
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; ; margin-left: 52.8pt;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">if the previous condition is not met but the age is 18:
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; margin-left: 52.8pt;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">write "You've finally grown enough for our application."
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; margin-left: 52.8pt;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Otherwise:
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: 'Noto Sans Symbols',sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; margin-left: 52.8pt;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">write "Welcome, have a good morning."
</li>
</ul>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">We continue with our virtual fan club of The Beatles. Look at the code, you will find the beginning of the program there: an input command that asks you to enter the name of the musician, accepts the answer from the user and returns the answer to a variable.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Add code to check if the user's answer is "Paul McCartney". When the user enters the name, write "yes" back.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task one: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT6exercise1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 1</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Ready?
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT6exercise1solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 1</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">...and now check that the user has typed the Ringo Starr's instrument correctly. If the user has entered the correct instrument (drums), display the word "excellent!" on the screen, otherwise "this is not the right instrument!&rdquo;.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">You already have a piece of code that will retrieve information from the user. :)
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to the second task: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT6exercise2EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 2</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Ready?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT6exercise2solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 2</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The Beatles have recorded 12 studio albums. Write a simple guessing game that will ask for this number. If the user enters a value less than 12, write "more", if the user enters a value greater than 12, write "less". In any other case, write "Bravo!".
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Note: the input function will always return a string. The code that we have written retrieves the answer and tries to convert it into a number. If this fails, Python will report an error. Remember to enter the correct numbers :).
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task three: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT6exercise3EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 3</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Ready?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT6exercise3solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 3</a>

Conditions

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Imagine writing a program in which you define two numeric variables and then check if the variables are even. Finally, you see a message about whether a number is even or not. It looks like this:

num1 = 2
num2 = 5
 
if num1 % 2 == 0:
    print("number", num1, "is even")
else:
    print("number", num1, "is odd")
 
if num2 % 2 == 0:
    print("number", num2, "is even")
else:
    print("number", num2, "is odd")

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT7sample1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">functions</a>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The code written above will work, but it's inefficient, because:
&nbsp;
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">we write practically the same code twice - we check num1 and num2 separately, conditions and messages are displayed identically,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">it is prone to errors - there can be a typo or a single equals sign in the equation operator (frequent error and difficult to notice).
</li>
</ul>

The best solution would be to write code "on the side" that checks the evenness of a number and use it when needed. Such a solution is possible! This is called a <span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #000000; font-weight: bold; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: baseline; white-space: pre-wrap;">function and is the basis of programming. Instead of writing the same thing several times, we can take the code we want to use repeatedly and convert it into a function:

def check_even(num):
    if num % 2 == 0:
        print("number", num, "is even")
    else:
        print("number", num, "is odd")

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">A function starts with a declaration which consists of:
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">def keyword,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">mandatory function name (here: check_even). You can name the function any way you like; the rules are the same as for naming variables (see lesson 1).
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">then in parentheses you can, if needed, specify the so-called function parameters; a parameter is a variable that you pass to a function and can use inside it
</li>
</ul>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">After the declaration, in the code block (remember to indent it) you place the commands, which will be executed after calling this function.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The rest of our program will look the following way:

num1 = 2
num2 = 5
 
check_even(num1)
check_even(num2)

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT7sample2EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">function statement</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Simple, isn't it?
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">That's not all!
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Sometimes we want the function to calculate something, for example, and the result to be passed on for further processing. For example, we have a list with prices of products in the shopping cart. We want to calculate the sum of these numbers and return it to the programmer, and the programmer will use it further. This is done as follows:

def sum_prices(nums):  # nums is a list
    result = 0
    for element in nums:
        result += element
    return result

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">What's going on here?&nbsp;
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">we define a function that we call sum_prices. This function takes the parameter nums. To make things easier, we assume that the programmer will always provide a list of numbers there.
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">we declare a result variable, which at the beginning of the function will have the value of 0. We will be adding subsequent numbers from the list to this value.
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">we create a loop that will iterate through all the elements of the nums list, and add each subsequent element to the result variable. As a result, after the loop is finished, the value of the result variable will be the sum of all the elements of the nums list.
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The last line of our function is the return result clause. This means that the function is to return the value of this variable to the programmer.
</li>
</ul>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">How to use it?
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">We can now call sum_prices function and assign its result to the variable:

my_list = [99.99, 119.99, 49.99, 29.99]
 
my_sum = sum_prices(my_list)
print(“The purchase price is”, my_sum, “euro.”)
 
Result:
The purchase price is 299.96 euro.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Do you rememberDo you remember how to check the length of the list from the lesson about lists? The len() function is used for this purpose, where we pass the list as a parameter. You can use this function, and then calculate the average price of goods from purchases.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://repl.it/@CodersLab/PYT7sample3"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">example with the function len()</a>

print(“Avarage product price is:”, my_sum / len(my_list), “euro.”)
 
Result:
Avarage product price is 74.99 euro.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Write a function named is_adult(), which takes a number as the parameter (for simplicity you can assume that the user will always enter a correct number). The function is to check if the age of the user is less than 18, in which case it should return False; otherwise - True.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to the first task: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT7exercise1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 1</a>
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Ready?
See solution: <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT7exercise1solutionEN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 1</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Write a function named is_beatle(), which will take a string as the parameter (for simplicity you can assume that the user will always enter a correct string). The function is to check if the given string is "John Lennon", "Paul McCartney", "Ringo Starr" or "George Harrison". If so, it will return True, otherwise - False.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Go to task two: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT7exercise2EN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Task 2</a>
Ready?
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See solution: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT7exercise2solutionEN#main.py"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to Task 2</a>

Functions

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Look how much we've learned! We already know all the programming elements needed to write something on our own: for example, a simple guessing game. The rules will be simple: the computer will come up with a number in the range from 1 to 10, and the task of the player will be to guess the number. The computer will tell us if our attempt was correct, or if the guessed number is greater or less than the number chosen by the computer. Before we do that, we have to learn three more simple things:

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In Python there is an input command, which takes a string as a parameter. This string is a message that will be displayed, and then the computer will wait for the user's response. After entering the information and pressing Enter, the input function returns the value that can be assigned to a variable.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">After following this instruction, the my_data variable will store the value entered by the user from the keyboard.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Note: this value is always a string, so we need to convert it to a number:

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The int function will attempt to convert the string to a number. If it fails, it will throw a ValueError. Those strings that consist only of digits, e.g. "11", "485", "228", but "11a", "1667.3" will be converted correctly, but "I am your father!" - will not! Of course, Python allows you to protect yourself against such erroneous values, but we won't deal with it in our tutorial because we would complicate it too much.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT8sample1EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #1155cc; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">the int function</a>

Python is distributed with a huge standard library. These additional functions, grouped into different sets, are not loaded into memory all at once it would take up much of the computer resources. They are, therefore, available at any time, but upon request - we need to import them.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">To make an import, we write at the beginning of the program:

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Why are we mentioning this now?

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Because this is how we will incorporate the randint function into our program, which will draw* a natural number from the range we provide. This function is located in a library called random. So in order to import it, we need to write the following line at the beginning of the program:

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Once we've done that, we can immediately use it:

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The above line will draw* a number from the range between 1 and 10.
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://repl.it/@CodersLab/PYT8sample2"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Drawing</a>

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">* In fact, the computer does not draw a number, it calculates it on the basis of a large set of data that constantly change (e.g. the time of a system clock). That is why such "drawn" numbers are called pseudo-random numbers.

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the chapter on loops, we learned how to create for - in loops, which are the most common way to loop our code. There is another loop in Python: while.
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">The while loop works as follows:
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">as long as the condition is fulfilled:
&nbsp;
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">do the body of the loop
</li>
</ul>

a = 1
while a < 10:
 print("a =", a)
 a += 1

<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">How does it work?
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the first line we declare the variable a, we give it the value of 1,
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Then we have the declaration of the while loop: it will be executed until a is less than 10. As soon as a reaches the value of 10, Python will exit the loop and move further.
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the next two lines (remember about the colon and indentation!) the body of the loop is executed: the value of the variable a is displayed, and then the variable a is incremented.
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">If not for the last line (a += 1), the variable would never change its value and therefore the condition a &lt; 10 would always be true. This would result in the infinite execution of the body of the loop.
</li>
</ul>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">See example: <a style="text-decoration: none;" href="https://replit.com/@CodersLab/PYT8sample3EN"><span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #0563c1; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: underline; -webkit-text-decoration-skip: none; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Loop while</a>

<ol style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: decimal; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">First import the randint function from the random library (see above).
</li>
<li dir="ltr" style="list-style-type: decimal; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Then draw* a number from 1 to 10 and assign it to the riddle variable.
</li>
<li dir="ltr" style="list-style-type: decimal; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Declare the guessed variable - give it the False logical value. This will be the so-called flag that we will raise (True) when the player will have guesses the number.
</li>
</ol>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Now it's time for something more difficult: start writing the while loop. Let's make this loop dependent on the condition guessed == False**. This means that the loop will be executed as long as the value of this variable is false, i.e. until the player has guesses the number. When they've guesses it, we will raise the flag and then Python will exit the loop.
&nbsp;
<ol style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;" start="4">
<li dir="ltr" style="list-style-type: decimal; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">In the body of the loop we take the response from the user, convert it from a string to a number, and check the following conditions:
</li>
</ol>
&nbsp;
<ul style="margin-top: 0; margin-bottom: 0; padding-inline-start: 48px;">
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">if the answer is less than the drawn number, we display the message "too little!&rdquo;
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">if the previous condition is not met, but the answer is greater than the drawn number - we display the message "too much!&rdquo;
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="1">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">if both the above cases are not true, it means that the user entered the correct number. We should then:
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="2">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">display the message "Great, that's the right number!",
</li>
<li dir="ltr" style="list-style-type: disc; font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline;" aria-level="2">
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">assign True value to the guessed variable; this will render the condition for executing the while loop unfulfilled and the program will exit the loop.
</li>
</ul>
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: bold; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">&nbsp;Done! You wrote your first program, congratulations!
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">Need a hint?
See the <a style="text-decoration-line: none;" href="https://replit.com/@CodersLab/PYT8exercise1solutionEN"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: #1155cc; font-variant-numeric: normal; font-variant-east-asian: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Solution to the </a>task
&nbsp;
<span style="font-size: 11pt; font-family: Calibri,sans-serif; color: #000000; background-color: transparent; font-weight: 400; font-style: normal; font-variant: normal; text-decoration: none; vertical-align: baseline; white-space: pre-wrap;">** You can write the same thing in a&nbsp; better way: not guessed. I decided to write it because I thought it would be more readable for a novice programmer.

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